EFFECT OF METHYLTHIOURACIL AND IODIDE ON THE IODINATED CONSTITUENTS OF THYROID TISSUE IN GRAVES' DISEASE

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Abstract
The distribu-tion of radioiodine amongst the various iodinated constituents of thyroid tissue was determined chromatographically in patients with Graves'' disease who had been treated with methylthiouracil for twenty days and then with iodide alone for ten days before thyroidectomy. Specimens of normal tissue from euthyroid patients with adenoma of the thyroid were used as controls. In the tissue from patients with hyperthyroidism the proportion of inorganic radioiodide was higher (28.8 per cent) than normal (8.1 per cent) and the ratio of radiomonoiodotyrosine to radio-diiodotyrosine (M/D) was higher (2.2) than normal (0.68). The latter could be explained in most cases by a block in iodine organification leading to a deficiency of iodine for the formation of diiodotyrosine. In 2 hyperthyroid patients, however, there was no apparent block in the organification of iodine. This block in the conversion of monoiodo-tyrosine to diiodotyrosine in the hyperthyroid human subject might have been the result of iodide therapy, but it seems more probable that it was a long-lasting effect of methylthiouracil.